The present invention relates to a power supply apparatus for supplying a power to various units and controlling an operation status of the unit.
Each of the related power supply apparatus assigns a rank to the unit to be supplied a power therefrom and supplies the power to the unit according to the rank.
The apparatus disclosed in Japanese Patent Application Laid-open No. 2004-208393 stops a power supply to load processing units of lower rank in case where the load of the load processing unit exceeds a predetermined value. Because the power supply to the load processing units of low ranks is stopped such way, the power can be kept supplied to other load processing units of higher ranks even when the system load is varied due to such a factor as an increase of the number of the processing units to be supplied a power.